Speaker
Description
Proper design of the calibration system is a crucial aspect to ensure the desired analysis performance of the currently built Hyper-Kamiokande detector. The National Centre for Nuclear Research (NCBJ) is building a linear accelerator (linac) that will provide electrons to calibrate the detector's energy. The overall energy calibration of the Hyper-Kamiokande detector based on the linac beam will be discussed, which is crucial for future low-energy measurements, such as solar or supernovae, as well as for higher-energy measurements, such as the JPARC beam or atmospheric neutrinos.
Linac design faces two challenges: its low electron beam energy, ranging from 3.5 MeV to 24 MeV, and the very low intensity of the desired electron beam at the level of single electrons, which need to be transported over long distances. The design of the linac system will be presented, along with the results of tests performed at NCBJ and some simulation studies. The poster presents the overall concept of the system along with all auxiliary components. The linac beam is transported over a distance of 100 m. Along its path, as it passes through a system of dipole magnets, the beam undergoes energy homogenization. Subsequently, through a controlled particle-reduction process, the beam is shaped so that exactly one electron reaches the output. Selected Monte Carlo simulation results regarding radiological safety for personnel and the general public will be displayed, alongside the impact of the output chamber geometry on electron detection by the sensors installed in the tank (the so-called shadowing effect). Unique solutions developed for this project, including the accelerator itself, the dipole magnet system with its vacuum chambers, and the beam transport system, will be presented in detail. The design of the output chamber and titanium foil, which serves as the vacuum-to-water barrier, will be presented. Due to calibration being performed at various depths, the foil must withstand pressure variations from 0 to 7 bar while minimizing impact on the exiting electrons. Results from tests conducted at NCBJ laboratories will be presented, focusing on target parameters such as the beam energy range, energy homogenization methods, and techniques for limiting the number of electrons emitted downstream of successive dipole magnets.
Furthermore, the poster will illustrate the installation and positioning of the beamline components operating inside the detector tank, which is another challenge, taking into account the dimensions of the Hyper-Kamiokande detector. The longest section, which inserts electrons into the tank, will be approximately 60 m. Finally, the Monte Carlo study of electrons from the linac propagated through the Hyper-Kamiokande detector will be presented.